Unexpected backslash

Hi!

- Version by `html2text --version`: 2020.1.16
- Test script: ` + direction`
- Python version `python --version` `Python 3.9.0`

Given ` + direction`, html2text give an unexpected backslash:
```
$ cat html
+ direction
$ html2text html
 \+ direction
```

This is due to ` + direction` received by `handle_data`, it's given to `escape_md_section`, which escapes the `+` to avoid it being interpreted as a unordered list item if I understand correctly. But here, the `+`, not being at the beginning of the line can't be interpreted as a list (or can it? ¹) so I think it should not be escaped, what do you think?

In fact there's cases where a list can be interepreted as so while not being sticked to the beginning of the line, for example in a quote:

> - a quoted
> - unordered
> - list

But - Here
its - not
a - list
no - need to escape